The present invention relates to a sheet material cutting device or cutter which cuts a sheet material by the cooperation of a circular rotary cutting blade moving while rotating and a fixed cutting blade formed into a long sheet.
In a printer for a terminal such as ECR or POS, a strip-shaped sheet material wound into a roll is pulled out for printing, and then the necessary portion is cut by a cutter into a sheet for delivery.
Various types of such sheet material cutters are available. The rotary-type cutter requires a high manufacturing cost and causes a relatively high degree of noise and therefore is now being replaced by a cutter based on a combination of a circular rotary cutting blade moving while rotating and a fixed cutting blade formed into a long sheet.
The prior art cutters of this type will be described below with reference to FIG. 11. A support 101 having a rotary cutting blade 102 horizontally travels on a screw shaft 100 as shown in FIG. 11 (a). As is clear from FIG. 11 (b), the rotary cutting blade 102 is rotatably bearing-supported on a shaft 105 which is on the support 101, and pressed against a fixed cutting blade 103 by means of a spring, for example. A sheet material transferred vertically in FIG. 11 (a) is cut by the rotary cutting blade 102 and the fixed cutting blade 103 while the support 101 travels horizontally.
In this cutter, it is important for ensuring satisfactory cutting to cause the rotary cutting blade 102 to slightly incline relative to the fixed cutting blade 103 as shown in FIGS. 12 and 13 so that the periphery of the rotary cutting blade 102 is brought into pressure-contact with the edge portion of the fixed cutting blade 103 at a point P in the travelling direction of the rotary cutting blade 102. Particularly, in order to permit cutting of the sheet material S not only during forward motion of the rotary cutting blade 102, but also during backward motion thereof, it is necessary to provide an apparatus having a means to switch over the inclination of the rotary cutting blade 102 between forward and backward motions. For example, Japanese Patent Publication No. 50-24,466 proposes such as apparatus.
This prior known cutter of sheet material will be described below. FIG. 14 is a perspective view illustrating a schematic construction of the conventional sheet material cutter, and FIG. 15 is a plan view illustrating the cutter of FIG. 14 as viewed from above. In these drawings, S is a sheet material such as paper; 41 is a fixed cutting blade in the form of a long sheet provided under the sheet material S; 41a is the upper surface of the fixed cutting blade 41, and 41b is the edge portion thereof; 42 is a guide rail installed so as to be in parallel with the edge portion 41b of the fixed cutting blade 41 above the sheet material S; 43 is a supporting member of a rotary cutting blade, which is loosely fitted in the guide rail 42; 44 is a rocking lever rockably fitted to the upper front portion of the rotary cutting blade supporting member 43; 45 is a pin making the rocking lever 44 rockable; 46 and 47 are pins limiting rocking of the rocking lever 44; 48 is a shaft fixed to the front portion of the rocking lever 5; 49 is a spring fitted in the shaft 48; 51 is the rotary cutting blade rotatably fitted to the tip of the shaft 48; 54 is a pin fixed to the upper rear end portion of the rocking lever 44; and 55a and 55b are wires secured each at an end to the pin 54.
Now, the operation of the prior known sheet material cutter having the construction as mentioned above will be described.
First, the sheet material S is fed in proximity to the upper surface 41a of the fixed cutting blade 41 and kept stationary there. The spring 49 presses the rotary cutting blade 51 with the edge portion directed forward, and as a result, the peripheral portion of the rotary cutting blade 51 is always in pressure-contact with the edge portion 41b of the fixed cutting blade 41. The wires 55a and 55b are stretched along the guide rail 42. These wires are adapted to be horizontally stretched alternately for each cutting step by means of a driving mechanism (not shown). FIG. 14 illustrates the wire 55b as pulled to the left. The rotary cutting blade supporting member 43 therefore travels by being pulled through the rocking lever 44 by the wire 55b in this direction. As a result, the rotary cutting blade 51 also travels to the left.
Upon this travel, the rocking lever 44 rocks clockwise around the pin 45, and the rear end portion of the rocking lever 44 comes into pressure-contact with the pin 47. Consequently, the rotary cutting blade 51 is kept in inclination of the end face thereof by an angle q relative to the edge portion 41b of the fixed cutting blade 41. The rotary cutting blade 5 therefore travels while keeping the leading head portion thereof in the travelling direction in point-contact with the edge portion 41b of the fixed cutting blade 41. Along with travel of the rotary cutting blade 51, the sheet material S is cut from right in FIG. 15 by the peripheral portion of the rotary cutting blade 51, which is in point-contact with the edge portion 41b of the fixed cutting blade 41.
Upon the completion of a cycle of cutting step as mentioned above, the wire 55 is pulled toward the right in FIG. 14. When the wire 55 is pulled toward the right in FIG. 14, then the rocking lever 44 rocks anti-clockwise around the pin 45. As a result, the rocking lever 44 brings the rear end portion thereof into pressure-contact with the pin 46. The end face of the rotary cutting blade 51 thus inclines in the direction opposite to that described above, so that the peripheral portion of the rotary cutting blade 51 comes into point-contact with the edge portion of the fixed cutting blade 41 at the right-hand portion thereof. The sheet material S in stoppage for a prescribed period of time is cut by the travel of the rotary cutting blade 51 to the right in FIG. 15.
In the above-mentioned cutter, however, it is necessary to provide wires horizontally stretched and a rocking lever rocking around a fulcrum shaft, and switching of the inclining direction of the rotary cutting blade requires a complicated construction, leading to an expensive apparatus.